1. Field of the Invention
The present invention relates to a lamp socket structure and particularly relates to a lamp socket structure for fitting a lamp that has no base, e.g., a wedge-base lamp.
2. Detailed Description of the Related Art
Prior to describing a conventional fitting structure, the wedge-base lamp will be described. The wedge-base lamp 1 can be made of glass and include a bulb portion 2a and a fixed portion 2b, as shown in FIG. 8. A filament 5 formed of tungsten or the like can be provided in a prescribed location inside the cylindrical bulb portion 2a, and is connected to the tip end of lead wires 4.
The lead wires 4 can be fixed with a stem 6 in the bulb portion 2a, sealed by the fixed part 2b, and guided outside from the bottom end of the bulb. The portions of the lead wires 4 that are guided outside are respectively folded to the surface side and the backside of the fixed portion 2b. 
In the fixed portion 2b, a plurality of protrusions 3 are integrally provided at predetermined positions. The wedge-base lamp does not have a base as provided in normal incandescent lamps.
The external diameter of the bulb portion can be changed from, for example, 10 mm, 13 mm, to 16 mm or the like to thereby increase the internal volume to change the brightness thereof The outer diameter dimension of the fixed portion remains unchanged in each of these configurations, so that a socket of a common dimension can correspond to lamps having a plurality of bulb diameters.
FIG. 8 to FIG. 10 show a conventional connection structure of a wedge-base lamp and a socket.
The socket 90 is configured to secure a wedge-base lamp 1 and to feed power thereto, and includes an opening 90a for receiving the wedge-base lamp, an outer peripheral portion 90b and a rear end portion 90c. Wedge-base lamp terminals 80 that are configured for feeding power to the wedge-base lamp can be inserted into the opening 90a side, and terminal feet 81 are disposed on the rear end portion 90c side, through a compartment portion 90d. 
The wedge-base lamp terminal 80 includes the terminal foot 81 and a terminal portion 82, and can be formed by pressing a metal plate by a die, and folding it. The metal plate can be made of, for example, copper alloy having a thickness of 0.3 mm. The terminal portion 82 includes feed pawls 82a that clamp the fixed part 2b of the wedge-base lamp 1 therebetween and are brought into contact with the lead wire 4. The tips of the feed pawls 82a can be folded inwardly three-dimensionally so as to face each other. The terminal foot 81 is connected to an external connection code via a connector (not shown) that is inserted from the rear end portion 90c side.
When the wedge-base lamp 1 is inserted into the socket opening 90a, as shown in FIG. 10, the feed pawls 82a clamp the fixed portion 2b of the wedge-base lamp 1 from opposite sides and are brought into contact with the lead wire 4 to feed power to the lamp.
Fixation and feeding of electricity are performed by inserting and fitting the wedge-base lamp to the socket. However, terminal feet 81 (i e., feed terminal) that extend downward can be provided for feeding electricity to the lower part of the socket. Accordingly, installation space for connection with a separate connector is required, and hence the size of the rear end portion 90c is relatively large. In addition, a relatively large space is required for fixation of the socket with a connector, causing a problem in that the depth dimension becomes large.
It is an object of the present invention to solve at least the above-described problems and to provide a fitting structure in which the depth dimension can be made small. In addition, it is an object of the invention to reduce the number of parts necessary to construct a socket and to reduce the overall cost of the socket.
In order to achieve the above-mentioned objects, according to a first aspect of the present invention, there is provided a wedge-base lamp fitting structure having a wedge-base lamp that includes a bulb portion, a fixed portion having no base and a lead wire at the fixed portion, a socket including an insertion portion for receiving and fitting the fixed portion therein, and a connector inserted and fitted into a rear end portion of the socket, wherein the socket includes an insertion portion having a rectangular cylindrical opening with substantially the same length as that of the fixed portion in an oblong rectangular shape, and a rear end portion provided on the back side of the insertion portion, with the insertion portion and the rear end portion being provided with a continuous opening. The insertion portion can have a side slit formed on the narrow side, with the opening having a plurality of pushing pieces and positioning protrusions provided therein. When the fixed portion of the wedge-base lamp is inserted into the opening in the insertion portion, the pushing pieces and positioning protrusions abut against the fixed portion of the wedge-base lamp, and the fixed portion is fixed with a gap between the inner face of the opening of the insertion portion and the lead wire, The connector formed in a separate body can be inserted and fitted into the gap through the opening in the rear end portion, to thereby connect a feed terminal provided in the connector and the lead wire.
According to an aspect of the invention, the wedge-base lamp is fixed by the socket, and secured more firmly by attaching the connector to the socket. Moreover, the feed terminal of the connector is connected to the lead wire of the wedge-base lamp. As a result, fitting becomes easier, and the depth dimension can be made smaller.
The above objects can be also achieved by a wedge-base lamp fitting structure according to other aspects of the present invention as described below.
According to another aspect of the present invention, there is provided the wedge-base lamp fitting structure, wherein the insertion portion and the rear end portion are integrally formed, both using a resin material having elasticity.
According to another aspect of the present invention, there is provided the wedge-base lamp fitting structure. wherein the depth of the side slit is substantially two thirds of the height of the fixed portion.
According to another aspect of the present invention, there is provided the wedge-base lamp fitting structure, wherein die pushing pieces are provided in each long side of the insertion portion. The positioning protrusions can be provided in at least three prescribed locations at positions on the rear end portion side than the pushing pieces, and a protrusion quantity of the positioning protrusion into the opening is smaller than a protrusion quantity of the pushing pieces.
According to another aspect of the present invention, there is provided the wedge-base lamp fitting structure, wherein the opening is made such that the sectional area in the rear end portion side is larger than that in the insertion portion.
The wedge-base lamp fitting structure can be formed integrally, thereby lowering cost. By making the depth of the slit about two thirds of the height of the fixed portion, the socket secures the wedge-base lamp with an adequate spring property, to thereby make the fitting workability with the connector easier. Since the pushing pieces can clamp the fixed portion from opposite sides at a position where the lead wire is provided in a prescribed location on the bulb side of the wedge-base lamp, and the fixed portion can also be secured by the positioning protrusions provided on the tip side of the fixed portion, play of the fixed portion can be reduced. The opening on the rear end portion side can also be made large, thereby enabling easy execution of the connection operation with the connector.